Your book makes it clear that the mine’s ventilation system was never up to the task.

Very little at Pike River was up to the task. The pipe that drained methane from the coal seam was under so much pressure that the men could hear the gas hissing, and the company had known for months that it urgently needed to be upgraded. Everyone knew that the ladder up the ventilation shaft was almost impossible to climb, yet it was still passed off as the mine’s emergency exit.

Critically important mining machinery was completely unfit for purpose, which held up production and destroyed morale. Training was inadequate, particularly for contractors. There was no systematic assessment of risks before Pike launched into the hydro-mining system in late September 2010. Gas monitoring was inadequate. The list goes on.

And that despite their public words, the management knew the 29 men were almost certainly dead after the first blast?

Rebecca Macfie.

Whether they knew or not, only they can say. What the book spells out is that there was abundant evidence at the time that the explosion was almost certainly unsurvivable.

The mine manager and mines rescue men had flown over the ventilation shaft in the hours after the explosion and it was obvious the surface fan had been severely damaged, indicating it had been an enormous blast. CCTV footage of the rush of debris out the portal had been seen that night by Pike, mines rescue and police staff. Everyone knew the mine was extremely small – it had barely started producing coal – so there wasn’t a large network of roadways to disperse the force of the blast.

By the morning after the explosion, it was known there was a fire burning in the mine, with carbon monoxide at unsurvivable levels. By day three it was confirmed that the compressed air line into the mine had ruptured.

Why did you want to write this book?

The prospect filled me with dread to be honest. The simple answer is that I was asked by Mary Varnham of Awa Press to do it. We didn’t get off to a great start because our first conversation about it was around lunchtime on February 22, 2011. We were still on the phone at 12.51, when there was a sudden violent upthrust and shaking that seemed to go on and on. I screamed and the phone went dead, and our lives descended into a strange period of chaos for a long time. I didn’t finally agree to do the book until about a year later.

In the end I decided to do it because Pike River is one of the most grievous stories of my generation. I felt that if I couldn’t make a decent contribution on this story, then my 25 years in journalism were worth zip.

You write that the story filled you with rage and grief. What aspect of the story makes you most angry?

The fact that it happened. This was the kind of disaster we would normally associate with a Third World country with weak institutions and poor governance. Yet it happened in New Zealand in 2010. As a mother or two, including a son who was almost 19 at the time, it was also a parent’s unbearable nightmare. I felt very deeply for those who had lost sons, husbands, fathers, brothers – men who had gone off to earn a living that day and never came home.

Did any part of your research bring you to tears?

Of course. I sat and talked to men with big tattooed forearms who wept in front of me, and mothers and wives who would talk bravely until they couldn’t contain their grief any longer. People were incredibly generous with their knowledge, but I knew that every time I interviewed an ex-Pike worker or family member or mines rescue man, I was taking them back into their pain. I often left people at the end of an interview wondering whether I was doing anyone any good.

Why is it so important to spend the money getting the bodies out – if any can be found? Two bodies are still in the Strongman Mine.

Relatively little money is being spent on the tunnel re-entry work – a very tiny fraction of the hundreds of millions spent on developing the mine that blew up and killed them.

Why is money spent on any occasion to recover bodies following tragedies? It was taken for granted that the two young climbers killed on Mt Taranaki would be retrieved, and that the bodies of plane crash victims Eric Hertz and his wife would be pulled from the sea. I have personally never endured anything like this, but I can understand that being able to see the evidence of death is an essential part of grieving and recovery for those who are bereaved.

That said, it’s clear that Solid Energy, the current owner of Pike, is also motivated by the fact that the 2.3km stone tunnel is one of the very few parts of the project that has economic value.

After years of taking returns out of the West Coast, do you think New Zealand Oil & Gas (NZOG), which owned 31% of the mine, has a moral responsibility to pay reparations to the families?

NZOG’s legal duty is to its shareholders, so its refusal to pay reparations is completely predictable. To be fair, NZOG did more than it was strictly obliged to do to help unsecured creditors after Pike went broke. And it’s not true to say NZOG took money out of the coast for years – Pike was a very disappointing investment and it was trying to get shot of it.

But NZOG was the architect of the project. It had wanted to get some value out of the Pike licence, which it had sat on for years, but it didn’t want to spend much money on proper geological investigation and feasibility studies. Hence, the whole thing was founded on flawed assumptions. NZOG was absolutely in the driving seat right through until Pike was floated on the share­market in 2007.

Morally, for NZOG to walk away and say “not my fault” is like a parent walking away from the trail of damage left by his or her destructive child.

You are a Cantabrian. Were you never tempted to instead write a story about Christchurch, on the CTV building, for instance?

I’ve written masses of stories on the post-earthquake Christchurch for the Listener. The two disasters have dominated my life and work for three years. Every time I went to the coast to cover the Pike Royal Commission in 2011, I would worry that we’d have another big shake and I wouldn’t be there for my daughter, who was in her last year at school, or that the city would be plunged into chaos yet again.

I made a conscious decision to focus on stories about the insurance, housing and social issues arising from the earthquake and stay away from the CTV story. I didn’t have enough mental or emotional resources to cover that as well as Pike. I also felt that Christchurch was unlikely to be ignored or forgotten at a political level, but without ongoing scrutiny the Pike story could very easily have been kicked under the carpet.

You went down a mine. Which one? What was it like? How far in did you go?

I went down the Terrace Mine in Reefton and Roa Mine near Blackball. I was underground at Terrace for hour or so. At Roa I spent most of a morning underground. When no machinery is working, it’s incredibly silent. When you turn out your cap lamp you literally can’t see your hand in front of your face. You see the movement of workers in the distance by the bright reflective stripes from their clothing, and when you stand and talk amid this darkness and silence there is an incredible sense of intimacy. I need sunshine, so I don’t think I could ever be a miner, but it helped me understand the sense of brotherhood that miners share.

Given how many coal mines still operate around the world, what lessons should be taken from Pike River?

That company directors need to understand the risks they are paid to oversee, that they need to have robust systems to scrutinise how those risks are being managed rather than taking their managers’ word for it, and that they need to exercise a genuine sense of inquiry and be alert to clues that challenge their assumptions.

Regulators need to understand the nature of catastrophic risk: when a plane malfunctions in the air, it’s likely everyone will die, which is why aviation has its own tight regulatory regime. When things go badly wrong in an underground coal mine, it’s likely everyone will die. Yet New Zealand lawmakers and regulators for nearly two decades treated the risks involved with coal mining as if they were much the same as running a florist.